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IntermediateBoat entry

Bob Mason Reef

Maryland, United States
Mid-Atlantic ocean wreck and reef diving off Maryland, Virginia and Delaware is exclusively boat-based and weather-dependent, with most sites 8-25+ miles offshore, so heavy fishing-charter and recreational boat traffic makes divers hard to spot at the surface; an SMB plus audible/visual signaling devices are strongly advised. Because these wrecks and reefs are intensively fished, snagged monofilament line, lead, hooks and netting are everywhere and create a serious entanglement risk, making a dive knife or line cutter essential. Currents are a defining hazardBoat entry7mm or semi-dry + hood typical

Boat dive — see Entry & access.

Bob Mason Reef at a glance

Bob Mason Reef is an intermediate boat dive site in Maryland, United States. Typically most favorable Jul · from 3 years of archive data. Divers commonly see Sheepshead, Scup (porgy), and Black sea bass. Recent reports put the water around 17°C (62°F). Check the latest conditions and entry details before you go.

Favorable window now· until 19:00 · sunset 18:07

Forecast for this hour · 15:00 · run 1 h ago
0.8 m (2.8 ft)waves — under a meter expected (waves — about three feet expected)

Tap a factor for its source and model point · Forecast 17°C · seasonal avg 19°C ( · Forecast 62°F · seasonal avg 67°F)

Site hazards: Mid-Atlantic ocean wreck and reef diving off Maryland, Virginia and Delaware is exclusively boat-based and weather-dependent, with most sites 8-25+ miles offshore, so heavy fishing-charter and recreational boat traffic makes divers hard to spot at the surface; an SMB plus audible/visual signaling devices are strongly advised. Because these wrecks and reefs are intensively fished, snagged monofilament line, lead, hooks and netting are everywhere and create a serious entanglement risk, making a dive knife or line cutter essential. Currents are a defining hazard

Read the full hazards ↓

Dive windows this week

Mon14:00–19:00 favorable

0.9 m waves · 4 kn wind (2.8 ft waves · 4 kn wind)

Tue8:00–19:00 favorable

0.8 m waves · 11 kn wind (2.6 ft waves · 11 kn wind)

Wed8:00–19:00 favorable

0.7 m waves · 7 kn wind (2.3 ft waves · 7 kn wind)

Thu8:00–19:00 favorable

0.5 m waves · 5 kn wind (1.8 ft waves · 5 kn wind)

Fri8:00–19:00 favorable

0.5 m waves · 6 kn wind (1.6 ft waves · 6 kn wind)

Sat8:00–19:00 favorable

0.5 m waves · 9 kn wind (1.7 ft waves · 9 kn wind)

Sun8:00–19:00 favorable

0.5 m waves · 12 kn wind (1.7 ft waves · 12 kn wind)

Favorable windowModerate window— no window

Every forecast dive window each day, site-local time, from wave and wind forecasts. Numbers under each bar are daylight averages.

First light 6:53 · Sunrise 7:20 · Sunset 18:07 · some windows run past sunset

Source: Open-Meteo marine · model point 15 km from site · updated 26 Oct, 13:23 GMT-4

Forecast only — always assess conditions on site.

Compare this weekend’s windows near Bob Mason Reef

Forecast · NOAA tide model

Tide & slack timing

Loading tide predictions

Recent diver reports

Dated firsthand observations from divers — not current conditions.

No diver reports for this site yet. — one dated observation helps every diver after you.

Dived here today — did the forecast match?

What Divers Say

Known for: Scup (porgy), Black sea bass, Tautog (blackfish)
Best time: Roughly May through October, with the calmest seas, warmest water and best visibility from June through September; spring and fall can offer the clearest water between weather systems, while winter diving is rare and weather-limited. Charters run primarily May-October.

Based on community reviews and site data. Conditions vary — always verify before diving.

Best months, historically

What conditions have historically been typical at this site, month by month — not a forecast.

  1. January, 71% of days have historically been favorable, water has typically been 6°C (42°F), waves have typically been 1.3 m (4.3 ft), wind has typically been 14 knots
  2. February, 67% of days have historically been favorable, water has typically been 6°C (42°F), waves have typically been 1.4 m (4.5 ft), wind has typically been 13 knots
  3. March, 63% of days have historically been favorable, water has typically been 8°C (47°F), waves have typically been 1.5 m (4.9 ft), wind has typically been 15 knots
  4. April, 77% of days have historically been favorable, water has typically been 12°C (54°F), waves have typically been 1.3 m (4.3 ft), wind has typically been 14 knots
  5. May, 85% of days have historically been favorable, water has typically been 17°C (62°F), waves have typically been 1.2 m (3.8 ft), wind has typically been 12 knots
  6. June, 92% of days have historically been favorable, water has typically been 22°C (71°F), waves have typically been 1.0 m (3.3 ft), wind has typically been 11 knots
  7. July, 98% of days have historically been favorable, water has typically been 25°C (77°F), waves have typically been 0.9 m (3.0 ft), wind has typically been 10 knots, historically most favorable
  8. August, 84% of days have historically been favorable, water has typically been 24°C (76°F), waves have typically been 1.2 m (3.9 ft), wind has typically been 11 knots
  9. September, 63% of days have historically been favorable, water has typically been 23°C (74°F), waves have typically been 1.5 m (5.0 ft), wind has typically been 12 knots
  10. October, 69% of days have historically been favorable, water has typically been 19°C (67°F), waves have typically been 1.5 m (4.8 ft), wind has typically been 12 knots
  11. November, 74% of days have historically been favorable, water has typically been 14°C (58°F), waves have typically been 1.2 m (3.9 ft), wind has typically been 12 knots
  12. December, 70% of days have historically been favorable, water has typically been 8°C (47°F), waves have typically been 1.3 m (4.4 ft), wind has typically been 13 knots

July has typically had the largest share of favorable days here. Conditions vary year to year — this is historical context, not a forecast.

Based on 3 years of archive data. Bar height shows the share of days each month whose conditions have historically scored favorably.

Marine life seen at this site

Species noted at this site — not a promise of what you’ll encounter.

Species seen here

Rough labels: “Commonly seen” usually means two or more recorded sightings near this site in public dive logs (GBIF), “Occasionally seen” one; “Seasonal” and “Rarely seen” come from dive-guide research. Not a measured rate.

Fills & rentals nearby

No dive shops mapped within 25 km (16 mi). Know one? Add it to the map.

Data updated June 2026

Site details

Artificial reef built from Designed units, 4 piles of 6 pyramids

reef

Mid-Atlantic ocean wreck and reef diving off Maryland, Virginia and Delaware is exclusively boat-based and weather-dependent, with most sites 8-25+ miles offshore, so heavy fishing-charter and recreational boat traffic makes divers hard to spot at the surface; an SMB plus audible/visual signaling devices are strongly advised. Because these wrecks and reefs are intensively fished, snagged monofilament line, lead, hooks and netting are everywhere and create a serious entanglement risk, making a dive knife or line cutter essential. Currents are a defining hazard — this stretch sits where the warm Gulf Stream meets the cold Labrador current, so currents can be strong and variable, divers often have to fight back to the anchor line, and free ascents risk being swept away from the boat. A pronounced summer thermocline is the norm, with comfortable high-60s to 70s+ water at the surface dropping sharply into the 50s-60s F below roughly 50 ft, where it is also much darker. Visibility is highly variable and usually limited, commonly 10-15 ft near the surface after Chesapeake/storm runoff and often 20-40 ft on the wreck, clearing toward 40-50 ft on the best Gulf Stream days; silt inside wreck structure is easily stirred up and can drop visibility to near zero. Depths frequently run 60-110+ ft, so it is easy to exceed recreational limits, and wreck steel is sharp and encrusted. Some sites are war graves (e.g., U-85, German-flag wartime wrecks) where penetration and artifact removal are prohibited, and a few historic wrecks may carry residual ordnance. Hurricanes and strong southerly/northeasterly weather routinely shut down or postpone diving.

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